The development of flash memory has been particularly rapid in recent years. Flash memory is a type of long-term non-volatile storage technology that does not require power to retain data, and has the advantages of high integration, fast access speed and easy to erase and rewrite. Therefore, it has a wide range of applications in many fields such as microcomputer, and automatic control, etc. To further increase the bit density in flash memory and, at the same time, to lower bit cost, a 3D NAND flash memory is proposed.
Referring to FIGS. 1-2, where FIG. 2 is a schematic diagram of a NAND flash memory shown in FIG. 1 along the cutting line in the AB direction, the NAND flash memory includes: a substrate 100; an isolation layer 103 formed on a surface of the substrate 100; a bottom selection gate 104 formed on the isolation layer 103; control gates 107 comprising a plurality of layers stacked together formed on the bottom selection gate 104; a top selection gate 109 formed on the control gates 107; a source line doping region 120 formed in the substrate between two adjacent rows of overlapping arrangement of the bottom selection gate 104, the control gates 107 and the top selection gate 109; a channel through hole (not labeled) penetrating the top selection gate 109, the control gates 107, the bottom selection gate 104 and the isolation layer 103; a channel layer 113 formed at side surfaces of the channel through hole; an insulation layer 115 formed on surface of the channel layer 113 in the channel through hole, where the insulation layer 115 fully fills the channel through hole; a bit line 111 formed on top surface of the channel layer 113; word line plugs 117 formed on the surface of each layer of the control gates 107; and word lines 119 formed on top of the word line plugs 117.
The adjacent bottom selection gate 104, control gates 107, top selection gate 109 and bit line 111 are isolated from each other by dielectric layers 106, which are not shown in FIG. 1.
However, the performance of such NAND flash memory fabricated with such existing techniques still needs to be improved. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.